Anchorage for prestress wire in concrete pipe



June 28, 1966 B- B. OHNSTAD 3,258,033

ANCHORAGE FOR PRESTRESS WIRE IN CONCRETE PIPE Filed April 25, 1965 2 Sheets-Sheet 1 ,1 "0 20 I m io 0 c INVENTOR. BURL. 5. OHMSTAD June 28, 1966 B. OHNSTAD 3,258,033

ANCHORAGE FOR PRESTRESS WIRE IN CONCRETE PIPE Filed April 25, 1963 3 Sheets-Sheet 2 INVENTOR. BURL B.OHN$ TAD ATZ'QBMLIL United States Patent 3,258,033 ANCHORAGE FOR PRESTRESS WIRE IN CONCRETE PIPE Burl B. Ohnstad, South Gate, Calif., assignor to American Pipe and Construction Co., Monterey Park, Calif, a

corporation of California Filed Apr. 25, 1963, Ser. No. 275,683 10 Claims. (Cl. 138-176) This invention relates to anchorage systems for securing the ends of high tensile steel wire wrapped under tension in the prestressing of concrete pipe.

In brief, the invention contemplates a novel embedment plate having a removable plug which is supported from a pipe form member during the initial pipe casting process. After the pipe is cast the plug is removed to leave a void for an anchor grip body. Both the anchor body and the plug which it replaces possess a lip por' tion extending beneath the ,embedment plate. The geometric relationship of the anchor body to the void formed in the surface of the pipe casting permits the body to be inserted therein but secures the body in a positive manner, preventing either rotation or pull-out by the tension of prestress wiring being Wrapped and tightened around a pipe casting.

It is a primary object of this invention to provide an improved anchorage for prestress wiring which is relatively inexpensive yet is easy to install, and will not pullout during tensioning.

Another object is to provide an improved anchorage comprising an embedment plate that can be formed by one simple stamping operation with no machining.

Another object of theinvention is to provide an improved anchorage comprising an embedm'ent plate having metal hooks stamped therefrom to leave slotted openings that increase the bond by interlocking the concrete onboth sides of the plate.

Other objects and advantages will become apparent in the course of the following detailed description.

In the drawings forming a part of this disclosure and in which like parts are designated by like reference numerals throughout the same,

FIG. 1 is a longitudinal section of a precast and reinforced concrete pipe that is formed with an anchorage for prestress wire as contemplated by this invention;

FIG. 2 is a plan view of the wire anchorage system employed with the concrete pipe of FIG. 1;

FIG. 3 is a section taken on line 3-3 of FIG. 2;

FIG. 4 is an end view of the concrete pipe as seen along line 44 of FIG. 1;

FIG. 5 is a perspective view of the anchor body used with the anchorage system;

FIG. 6 is a section like that of FIG. 3 but taken through a pipe form member prior to casting cementitious material into the pipe form;

FIG. 7 is a perspective view of a removable plug used in the process of embedding an anchor plate in a concrete pipe. as shown in FIG. 6; and

FIG. 8 is a perspective view of the anchor plate used in the anchorage system described.

Referring to FIG. 1, there is illustrated a precastconcrete pipe 10, comprising a main body portion 11 and high tensile reinforcing wire 12 embedded in an exterior concrete layer 13. This invention is principally directed for embedding plate member 15 in main body portion 11 while said body portion is being cast in a pipe form including an outer barrier plate 17.

Referring to FIG. 8, anchor plate member 15 is integrally formed from a single piece of metal plate and includes a pair of arms 20 and 21 that extend outward from an intermediate and offset center portion 22. The center portion, it will be noted, has an opening 23 there in for receiving anchor body 16 therethrough. Plate member 15 further includes an anchor body support arm 24 which extends from an edge of opening 23 and being disposed in spaced relation below said opening. A threaded opening is provided on arm 24, as by means of nut 25, to permit mounting of anchor plate 15 from barrier plate 17.

Each of the plate arms 20 and 21 is formed with an integral tongue 20a and 21a, respectively, that is pressed out of the plate material from which plate 15 is made; and the free end of each tongue extends toward the other. This configuration of plate 15 insures positive anchorage thereof in the body portion 11. Moreover, the method of integrally forming tongues 20a or 21a by pressing them out of the arms 20 and 21 results in a very low cost of manufacture. The same advantage is also obtained by pressing arm 24 out of center portion 22.

The apparatus and method of embedding anchor plate 15 in body portion llis illustrated in FIG. 6. Before filling the pipe form with concrete, anchor plate 15 is attached to the outer barrier plate 17 by means of a bolt 26 which extends through the barrier plate and threadedly engages nut 25. However, even before mounting plate 15 in the indicated fashion, a pliable insert or removable plug 27 is placed into the cavity which is later filled and occupied by anchor body 16. Importantly, plug 27 includes a lip portion 28 that extends beneath the anchorage plate on the side of opening 23 opposite to the side to which arm 24 is integrally formed. While supported upon arm 24, plug 27 closes over opening 23 and presents an exterior surface 29 substantially coplanar with the surface of center portion 22,- which is held against barrier plate 17 by bolt 26.

It will be noted that plug 27, which may be made of neoprene, is formed with an opening therethrough that receives a bushing 30; and the opening is alignable with the axis of nut 25 to form a connecting passage for bolt 26.

After body portion 11 of pipe 10 has been cast (with anchor plate 15 and insert 27 being embedded therein) the pipe form including barrier 17 is dismantled. Both 26 is, of course, unthreaded from nut 25, and plug 27 is removed. This opens the cavity into which anchor body 16 may then be placed.

Referring to FIG. 5, anchor body 16 is formed in substantially a conventional manner in that it provides a slotted passage 31 for gripping a wire. The opposed rack-like surfaces of passage 31 serve to grip the wire which is forced into the passage as by hammering. Unlike conventional anchor bodies, however, body 16 is provided with a lip 32 to fill the void created by removal of lip 28 on plug 27; and the portion of body 16 above center portion 22 is made substantially equal to the diameter of wire 12.

Accordingly, anchor body 16 can be inserted through opening 23 of plate 15 in one position only, namely with lip 32 fitting under one edge of the plate. This arrangement secures the anchor body in a positive manner, preventing either rotation or pull-out by the tension of prestressing wire 12. Furthermore, because the top surface of anchor body 16 is flush with the top of the wire 12, body 16 is inherently protected against corrosion to the same degree as prestress wire 12.

Additional advantages may be seen in that anchor body 16 is inserted and secured within a precast void in the pipe wall without welding, bolting, or the use of special tools. Also, embedment plate 15 can be formed by one simple stamping operation with no machining and practically no welding; the slotted holes in the plate increase the bond by interlocking the concrete on both sides of the plate; and although many conventional anchorage systems require that the prestress wire be wrapped under reduced tension (to avoid anchor failure), the anchorage 14 will not fail under a tensile force equal to the ultimate strength of the normal prestress wire.

It is to be understood that although a preferred embodiment of the invention is shown and described, various changes may be made without departing from the spirit of the invention or the scope of the attached claims, and each of such changes is contemplated.

What I claim and desire to secure by Letters Patent 1. An anchorage for prestressing wire to be embedded in concrete pipe, comprising: a plate member having a pair of arms extending outwardly from an intermediate and offset center portion, each of said arms having an integral tongue pressed therefrom, the free end of each tongue extending toward the other; said center portion having an opening therein for receiving an anchor body therethrough; said plate member having an anchor body support arm attached thereto in spaced relation below said opening.

2. The anchorage of claim 1 wherein said anchor body support arm includes means defining a threaded opening, permitting said plate member to be mounted from the interior of a pipe form barrier.

3. The anchorage of claim 1 wherein said anchor body support arm extends from an edge of said opening in said center portion, being formed of material pressed from said opening.

4. An anchorage device which comprises: a plate member having a pair of arms extending in opposite directions from an intermediate and offset center portion, each of said arms having a tongue integral therewith, each of said tongues being deflected from the plane defined by said arms with the free end of each tongue extending toward the free end of the other tongue, said center portion having an opening therein for receiving an anchor body therethrough, said plate member having an anchor body support arm attached thereto and extending in spaced relation from said offset center portion on the side of said portion opposite the direction of said oflset.

5. The anchorage of claim 4 wherein said anchor body support arm includes a threaded opening having an axis extending through said openings in said oflset center portion.

6. The anchorage of claim 4 wherein said anchor body support arm extends from an edge of said opening in said center portion, said arm being formed of material pressed from said opening.

7. An anchorage device which comprises: a plate member having a pair of arms extending in opposite directions from an intermediate and offset center portion, each of said arms having a tongue integral therewith, each of said tongues being deflected from the plane defined by said arms with the free end of each tongue extending toward the free end of the other tongue, said center portion having an opening therein for receiving an anchor body therethrough, said plate member furthere having an anchor body support arm extending from an edge of said opening in said center portion in spaced relation from said offset center portion on the side of said portion opposite the direction of said oifset and being formed from material pressed from said opening, said arm including a threaded opening having an axis extending through said opening in said oflset center portion.

8. A concrete pipe having a longitudinal axis, which includes: a plate member having a pair of arms extending outwardly from an intermediate and offset center portion, said center portion having an opening therein for receiving an anchor body therethrough, said plate member having an anchor body support arm attached thereto in spaced relation below said opening, said member being embedded in said pipe transversely to said longitudinal axis with said offset center portion lying substantially in the plane defined by the outside surface of said pipe.

9. The concrete pipe of claim 8 wherein each of said arms has a tongue extending therefrom.

10. The concrete pipe of claim 8 wherein each of said arms of said plate member has a tongue integral therewith, each of said tongues being deflected from the plane defined by said arms with the free end of each tongue extending toward the free end of the other tongue.

References Cited by the Examiner UNITED STATES PATENTS 1,187,918 6/1916 Meyer -Q 52 700 1,280,485 10/1918 Kahn 52 710 2,887,130 5/1959 Kell 52-224 FOREIGN PATENTS 195,324 3/1923 Great Britain.

FRANK L. ABBOTT, Primary Examiner.

HENRY C. SUTHERLAND, Examiner.

I. L. RIDGILL, Assistant Examiner. 

8. A CONCRETE PIPE HAVING A LONGITUDINAL AXIS, WHEN INCLUDES: A PLATE MEMBER HAVING A PAIR OF ARMS EXTENDING OUTWARDLY FROM AN INTERMEDIATE AND OFFSET CENTER PORTION, SAID CENTER PORTION HAVING AN OPENING THEREIN FOR RECEIVING AN ANCHOR BODY THERETHROUGH, SAID PLATE MEMBER HAVING AN ANCHOR BODY SUPPORT ARM ATTACHED THERETO IN SPACED RELATION BELOW SAID OPENING, SAID MEMBER BEING EMBEDDED IN SAID PIPE TRANSVERSELY TO SAID LONGITUDINAL AXIS WITH SAID OFFSET CENTER PORTION LYING SUBSTANTIALLY IN THE PLANE DEFINED BY THE OUTSIDE SURFACE OF SAID PIPE. 